I work in a software development company and our ticket system is based on Jira. I asked my collegues why I cannot use Markdown it ticket comments but they couldn't help me. So I started my own research and came across this thread:
https://community.atlassian.com/t5/Jira-questions/Using-markdown-in-Jira/qaq-p/892041
with this nice screenshot provided by Daniel:

I carefully explored the UI and cannot confirm that I see any attributes of the Markdown presence 
So I wonder - is it really supported or not, and if yes - how to enable it?
P.S. Sorry, I cannot give a definite reply in the "Hosting type" field below, but I can say that we access our Jira through a third-party domain. If it helps or even makes any sense for you 